1. Field of the Invention
The present invention relates to a check valve for allowing the flow of fluid in one direction only and also relates to a brake hydraulic pressure control device incorporating the check valve.
2. Discussion of the Related Art
Heretofore, in check valves that a ball is selectively seated on a valve seat surface for opening and closing a fluid passage, the ball (valve member) is urged by a coil spring (resilient member) toward the valve seat surface (i.e., in the valve closing direction). When the pressure on an upstream side of the valve seat surface increases a predetermined pressure or higher beyond the pressure on a downstream side of the valve seat surface, the ball leaves the valve seat surface against the resilient force of the coil spring to open the valve, so that fluid flows in a predetermined one direction. During the opening of the valve, a force caused by the flow of fluid and the resilient force of the coil spring are exerted on the ball, and thus, the ball is moved to a position where both of the forces are in balance.
For example, in a check valve disclosed in U.S. Pat. No. 6,910,745 B2 (equivalent of JP2004-19805 A), as shown in FIG. 3 of the patent, a compression coil spring 560 is used as resilient member, and a ball-like valve member 540 is urged by the compression coil spring 560 to be seated on the valve seat surface 504. The compression coil spring 560 is arranged so that the direction in which the compression coil spring 560 urges the valve member 540 is inclined at a predetermined angle relative to the direction in which the valve member 540 receives the pressure of fluid. Thus, at the time of a valve opening that the valve member 540 leaves the valve seat surface 504, the valve member 540 is pressed by the compression coil spring 560 which is arranged to be inclined, against a side wall surface 526, so that vibration such as resonance can be suppressed.
Further, in a check valve (outlet valve 17) disclosed in U.S. Pat. No. 5,232,273 (equivalent of JP 5-87043 A), as shown in FIG. 1 of the patent, a plate spring is used as resilient member for the purpose of reducing the height of the check valve. A sphere 50 being a ball-like valve member is urged by two plate or leaf spring tongue portions 57 toward a valve seat 51. The plate spring has a ring-like circumference, and the two leaf spring tongue portions 57 are formed to extend respectively from radially opposite positions of a ring internal portion toward the ring center and are in contact with the sphere 50 to urge the same.
However, in the prior art check valve disclosed in the first mentioned patent, there arise a problem that the use of the compression coil spring 560 results in a large space required for installation as well as a high cost.
Further, in the prior art check valve disclosed in the second mentioned patent, the sphere 50 as valve member is urged by the two leaf spring tongue portions 57 of a spring body 55 in a valve closing direction from one side only. At the time of a valve opening, since the two leaf spring tongue portions 57 equally urge the sphere 50 in the axial direction, it may be the case that when the sphere 50 leaves the valve seat 51 and is balanced by the pressure of fluid, the sphere 50 is brought into an unstable floating state and vibrates due to the pulsation or the like in the fluid discharged from a pump. Further, although the two leaf spring tongue portions 57 of the spring body 55 are flexed in the valve opening direction by being pushed by the sphere 50, the known check valve is not provided with any stop portions which limit the flex movements of the leaf spring tongue portions 57. Thus, there arises an anxiety that the leaf spring tongue portions 57 are strained over the allowable stress thereof to be destroyed.